A continuing goal in integrated circuitry fabrication is to form the circuitry components to be smaller and denser over a given area of a semiconductor substrate. One common electronic circuit device is a capacitor, which has a capacitor dielectric region received between a pair of conductive electrodes. In such devices, there is a continuing challenge to maintain sufficiently high storage capacitance despite decreasing area in the denser circuits. Additionally, there is a continuing goal to further decrease horizontal area occupied by the capacitor. One manner of increasing capacitance is through cell structure techniques, for example forming trench or stacked capacitors.
Highly integrated memory devices, for example 256 Mbit DRAMs and beyond, are expected to require a very thin dielectric film for cylindrically stacked, trenched or other capacitor structures. To meet this requirement, the capacitor dielectric film thickness will be below 2.5 nanometer of SiO2 equivalent thickness. Accordingly, materials other than SiO2 having higher dielectric constants are expected to be used. Si3N4 is one such material which has been used either alone or in combination with silicon dioxide as a capacitor dielectric region. Insulating inorganic metal oxide materials, for example Al2O3, Ta2O5 and barium strontium titanate, have even higher dielectric constants and low leakage currents which make them attractive as capacitor dielectric materials for high density DRAMs, non-volatile memories and other integrated circuitry.
In many such applications, it would be highly desirable to utilize metal for the capacitor electrodes, thus forming a metal-insulator-metal (MIM) capacitor. Exemplary proposed metals include platinum, rhodium, ruthenium, palladium and iridium. Such might be utilized in elemental and/or alloy form in many instances.
The ever increasing density in the fabrication of integrated circuitry is resulting in individual devices occupying less horizontal area at the expense of an increase in the vertical, or orthogonal, dimension of the individual devices. One common and typical capacitor construction includes a container-shaped capacitor where at least one of the capacitor electrodes has a container or cup-like shape. An example manner of forming such containers is to initially form a capacitor opening within an insulative layer. One or more conductive capacitor electrode layers are then deposited to less than fill and to line the opening. The conductive layer or layers are typically then planarized back relative to the insulative layer(s), thus forming a container-shaped capacitor electrode.
One or more capacitor dielectric layers are then conformally deposited over the container-shaped electrode. One manner of doing so includes chemical vapor deposition using a metallorganic deposition precursor. In the context of this document, a “metallorganic” is any organic molecule having a metal constituting a part thereof. Unfortunately, platinum, rhodium, iridium, ruthenium and palladium can have a catalytic effect on the decomposition of certain metallorganic precursors. In many applications, it has been found that a capacitor dielectric layer formed by chemical vapor deposition utilizing a metallorganic precursor over an outer capacitor surface having at least one of these metals in elemental and/or alloy form has a tendency to deposit considerably thicker at the upper portions of the container. This can result in a bread-loafing effect, and in some instances to an extreme of depositing essentially none of the capacitor dielectric material towards the bottom half of the container. It is theorized that, perhaps, these metals are catalyzing decomposition of the metallorganic precursor restricting or precluding their deposit of a desired capacitor dielectric layer at the bottom portions of the containers.
While the invention was motivated in addressing the above-described issues, it is in no way so limited. The invention is only limited by the accompanying claims as literally worded, without interpretative or other limiting reference to the specification, and in accordance with the doctrine of equivalents.